This invention relates to the sealing of leaks, and more particularly to a leak sealing patch and a hand tool for applying such a patch to a fluid containing body and to methods using such a tool and patch. Prior leak sealing tools and methods, as exemplified by U.S. Pat. No. 3,645,816, required that the surface area surrounding a leak be thoroughly cleaned before a patch could be applied, and also that any fluid pressure within the leaking body be eliminated by draining fluid from the body. Also, the tools used to apply leak seal patches were made from rigid materials that could not be deformed to conform to the shape of the surface area around the leak. This made it necessary to have a plurality of tools for applying patches with each tool having a shape conforming to a single specific area or contour.